Systems and methods for fuel filter diagnostics

Abstract

Methods and systems are provided for controlling a fuel system of a vehicle to diagnose whether a fuel filter is functioning as desired. In one example, a method may include, in response to a fuel rail pressure decreasing below a threshold pressure while an engine of the vehicle is running, diagnosing whether degradation of fuel injectors or a fuel pressure regulator of the vehicle has occurred while the engine is not running. Then, only if degradation of the fuel injectors and fuel pressure regulator has not occurred, a fuel filter cleaning routine is performed.

The invention claimed is: 
     
       1. A method, comprising:
 responsive to an engine fuel rail pressure decreasing below a threshold pressure, determining degradation of any of a plurality of engine fuel system components including a fuel injector, a fuel regulator, and a fuel line coupled to a fuel pump; 
 if the determining of degradation determines degradation of any of the plurality of engine fuel system components has occurred, indicating the degradation without performing a fuel filter cleaning routine; 
 if the determining of degradation does not determine degradation of any of the plurality of engine fuel system components has occurred, then adjusting operation of the fuel pump to perform the fuel filter cleaning routine, and following performance of the fuel filter cleaning routine, responsive to the engine fuel rail pressure remaining below the threshold pressure, indicating fuel system degradation. 
 
     
     
       2. The method of  claim 1 , wherein adjusting operation of the fuel pump to perform the fuel filter cleaning routine includes performing a plurality of fuel pulse cycles throughout a cycling duration, with the fuel pump and the fuel filter being disposed within a fuel tank. 
     
     
       3. The method of  claim 2 , wherein each fuel pulse cycle of the plurality of fuel pulse cycles includes pulsing fuel through the fuel pump and the fuel filter in a forward direction and, after pulsing fuel through the vehicle fuel pump and the fuel filter in the forward direction, pulsing fuel through the fuel pump and the fuel filter in a reverse direction opposite to the forward direction and away from a fuel rail. 
     
     
       4. The method of  claim 3 , wherein pulsing the fuel through the fuel pump and the fuel filter in the reverse direction includes providing a negative electrical voltage to the fuel pump. 
     
     
       5. The method of  claim 1 , wherein determining whether degradation of any of the plurality of engine fuel system components has occurred includes:
 operating the fuel pump in a forward direction for a flow duration to flow fuel to the engine fuel rail; and 
 while operating the fuel pump in the forward direction for the flow duration:
 diagnosing degradation of the fuel injector by adjusting operation of the fuel injector and determining an air/fuel ratio in an exhaust passage of the engine; and 
 diagnosing degradation of the fuel regulator or the fuel line by determining a vapor pressure in a fuel tank while sealing the fuel tank from atmosphere, the fuel regulator and the fuel pump and the fuel line each positioned within the fuel tank. 
 
 
     
     
       6. The method of  claim 5 , wherein operating the fuel pump in the forward direction includes providing a positive electrical voltage to the fuel pump. 
     
     
       7. The method of  claim 5 , wherein adjusting operation of the fuel injector includes fully closing a nozzle of the fuel injector throughout the duration and not opening the nozzle throughout the duration. 
     
     
       8. The method of  claim 5 , wherein determining the vapor pressure in the fuel tank includes measuring the vapor pressure via a vapor pressure sensor coupled to the fuel tank. 
     
     
       9. The method of  claim 5 , wherein sealing the fuel tank from atmosphere includes moving a fuel tank isolation valve to a fully closed position. 
     
     
       10. The method of  claim 5 , wherein determining the air/fuel ratio includes measuring the air/fuel ratio via one or more sensors coupled to the exhaust passage. 
     
     
       11. The method of  claim 10 , wherein measuring the air/fuel ratio via the one or more sensors includes measuring an amount of oxygen in the exhaust passage via a heated exhaust gas oxygen sensor. 
     
     
       12. A method, comprising:
 operating an engine of a vehicle for a first duration and comparing a pressure of fuel in an engine fuel rail to a threshold pressure throughout the first duration; and 
 responsive to both of the pressure of fuel in the engine fuel rail decreasing below the threshold pressure at least once during the first duration and an engine key-off request:
 running the engine unfueled for a second duration while monitoring an air/fuel ratio in an exhaust passage coupled to the engine throughout the second duration; 
 sealing an engine evaporative emissions system coupled to a fuel tank of the vehicle and monitoring a fuel vapor pressure within the fuel tank for a third duration; and 
 adjusting operation of a fuel pump coupled between the fuel tank and the fuel rail responsive to both of the air/fuel ratio and the fuel vapor pressure, wherein
 in response to the air/fuel ratio being less than a threshold air/fuel ratio or the fuel vapor pressure being greater than a threshold fuel vapor pressure, stopping a flow of fuel through the fuel pump; and 
 in response to the air/fuel ratio being greater than a threshold air/fuel ratio for the second duration and the fuel vapor pressure being less than a threshold fuel vapor pressure for the third duration, pumping fuel in a reverse direction of the fuel pump through a fuel filter. 
 
 
 
     
     
       13. The method of  claim 12 , wherein pumping fuel in the reverse direction of the fuel pump includes flowing fuel from an outlet of the fuel pump to an inlet of the fuel pump, the outlet fluidly coupling the fuel pump to the engine fuel rail via a fuel line, the inlet fluidly coupling the fuel pump to the fuel filter and fuel stored within the fuel tank. 
     
     
       14. The method of  claim 12 , wherein pumping the fuel in the reverse direction of the fuel pump through the fuel filter occurs during each pulse of a plurality of pulses of fuel through the fuel pump and the fuel filter. 
     
     
       15. The method of  claim 14 , wherein each pulse of the plurality of pulses further includes pumping fuel in a forward direction of the fuel pump opposite to the reverse direction, before pumping fuel in the reverse direction. 
     
     
       16. A system, comprising:
 an engine; 
 a fuel rail including a plurality of fuel injectors coupled to cylinders of the engine; 
 a fuel tank having a fuel pump and a fuel filter disposed therein, the fuel pump fluidly coupled to the fuel rail; 
 a plurality of fuel tank pressurized components consisting of a fuel pressure regulator and one or more fuel lines disposed within the fuel tank; and 
 an electronic controller including first computer readable instructions stored on non-transitory memory that when executed cause the controller to:
 determine whether a fuel rail pressure is less than a threshold fuel rail pressure before an engine key-off request and while the engine is running and combusting fuel/air; and 
 after the engine key-off request and before an engine key-on request with no other engine key-on requests therebetween, in response to the fuel rail pressure being less than the threshold fuel rail pressure:
 determine whether degradation of one or more fuel injectors of the plurality of fuel injectors has occurred; 
 determine whether degradation of any of the plurality of fuel tank pressurized components has occurred; 
 in response to determining that degradation of the one or more fuel injectors or any of the plurality of fuel tank pressurized components has occurred, indicating degradation of a fuel system component without performing a fuel filter cleaning routine; and 
 in response to determining that degradation of the one or more fuel injectors has not occurred and degradation of any of the plurality of fuel tank pressurized components has not occurred, performing the fuel filter cleaning routine. 
 
 
 
     
     
       17. The system of  claim 16 , further comprising an electrical circuit coupling the fuel pump to a power source, the electrical circuit including a first set of switches coupled to a first voltage input and a second set of switches coupled to a second voltage input, and further comprising second computer readable instructions stored on the non-transitory memory that when executed cause the controller to:
 while performing the fuel filter cleaning routine, provide a plurality of pulses of fuel through the fuel pump, where each pulse of the plurality of pulses includes flowing fuel in a forward direction of the fuel pump and then flowing fuel in a reverse direction of the fuel pump, where flowing fuel in the forward direction includes opening the first set of switches and closing the second set of switches in order to flow electrical current through the fuel pump in a first direction, and where flowing fuel in the reverse direction includes closing the first set of switches and opening the second set of switches in order to flow electrical current through the fuel pump in an opposite, second direction. 
 
     
     
       18. The system of  claim 17 , further comprising a first check valve and a second check valve fluidly coupled in parallel to an outlet of the fuel pump downstream of the outlet and upstream of the fuel pressure regulator, the first check valve adjustable to a fully opened position in response to a fuel flow from the fuel pump in a forward direction of the fuel pump and not adjustable to the fully opened position in response to a fuel flow from the fuel pump in a reverse direction of the fuel pump, and the second check valve adjustable to a fully opened position in response to the fuel flow from the fuel pump in the reverse direction of the fuel pump and not adjustable to the fully opened position in response to the fuel flow from the fuel pump in the forward direction of the fuel pump.